A conventional pneumatic tin sucker as shown in FIG. 1 comprises a housing 1, a piston rod 11 in the housing 1, a push button 12 with a lower bar 13 on top of the rod 11, a release button 14 below the bar 13, a piston 15 connected with the piston rod 11, a release button 14, and a coil spring 16 under the piston 15. After the whole tin sucker is assembled, the push button 12 is pressed to push down the piston 15 to compress the spring 16, and the bar 13 fits with the release button 14. In this condition, a sucking nozzle 17 is moved near molten tin scrap and the release button 14 is pressed down, permitting the spring 16 to recover and push up the piston rod 11 and the piston 15 in the housing 1 so that the tin scrap may be sucked through the nozzle 17 into the housing 1.
However, the conventional tin sucker has several inconveniences. The push button 12 has to be forcefully pressed down with a thumb every time the sucker is used. A thumb will hurt after frequent use. The release button also has to be pressed down, in addition to pressing of the push button to finish the sucking operation. Consequently, molten tin scrap might solidify before being sucked by the sucker.
There is in the prior art a tin sucker combined with a vacuum pump or air compressor for producing a large sucking force. It involves a very high cost and a large number of components, and is not popular for most users.